Is Jim Matheson a liberal or a moderate?

Jim Matheson presents himself to voters as a moderate willing to work with both parties. Critics from the right contend that he’s really a liberal at heart who will promptly ally with Pelosi and Obama when given the chance. It’s time for some hard data.

How we measure US Representatives’ ideology

Political scientists have worked for years to develop reliable ways of estimating the ideology of members of Congress. The best technique produces so-called DW-NOMINATE scores, available for download at VoteView.com. (Regular readers will recall that I used a similar method to estimate ideology scores of Utah’s state legislators.) The DW-NOMINATE algorithm uses all votes cast by members of Congress to line them up from most liberal to most conservative, with scores ranging from -1 (most liberal) to +1 (most conservative).

I stress that -1 does NOT mean “perfect Democrat” and +1 does NOT mean “perfect Republican,” as it’s entirely possible for a person to be far left of the Democrats or far right of the Republicans. These are relative scores, not absolute scores.

Below, you can see how the scores look for the current (112th) US House. The line goes up where there is a greater concentration of scores. You’ll see that there is a big concentration around -0.5 and also around +0.5. This reflects the polarization of the two major parties, with few Representatives in the center.

Distribution of ideology scores in the 112th US House

If I drew a separate line for each party, rather than using one line for all representatives, it would look like this:

Distribution of ideology scores by party in the 112th US House

The two lines don’t overlap at all. That’s because the most liberal Republican is somewhat more conservative than the most conservative Democrat. (It was common for the lines to overlap a couple decades ago, but that’s another story.)

How Matheson, Bishop, and Chaffetz compare to their parties

Now, let’s go one step further and mark Jim Matheson’s location. Just for comparison, we’ll also add in Rob Bishop and Jason Chaffetz.

Ideological location of Utah’s US Representatives relative to other Representatives

It is readily apparent that Matheson is among the most conservative Democrats in the US House. Of 194 Democrats presently serving, only 4 have a score more conservative than Matheson’s. Whether that makes him a “conservative” in absolute terms rather than relative terms is, of course, in the eye of the beholder.

Incidentally, Nancy Pelosi’s score of -0.533 places her well left of center even within the Democratic Party. Fewer than one-quarter of House Democrats are more liberal than Pelosi. There is noticeable ideological daylight between Pelosi and Matheson.

For discussion of Bishop and Chaffetz, read the footnote at the end of this sentence.1

How ideological (or predictable) is Matheson?

The DW-NOMINATE scores also give us an estimate of each Representative’s overall predictability. For most Representatives, you can do a pretty good job of predicting their vote on any particular bill simply by knowing the Representative’s DW-NOMINATE score (and also by knowing how the other 434 members of the House voted on the bill in question).

Usually, predictability is pretty high. As you can see from the chart below, you can predict Rob Bishop’s vote 92% of the time and Jason Chaffetz’s vote 93% of the time. These are typical scores. In fact, Chaffetz sits exactly on the median.

Data from the 112th US House

Jim Matheson, meanwhile, is hard to pin down. You can predict his vote only 78% of the time. That might sound high in absolute terms, but in the highly polarized environment of the US House, that’s a remarkably low score. Only 5 of the 435 Representatives have a lower predictability score. From a statistical standpoint, this low predictability score suggests that Matheson’s Congressional votes often go against partisan expectations.

Of course, this analysis does not attempt to address whether Matheson’s voting record is consistent with what voters in Utah’s fourth district desire. Only voters themselves can answer that question.

Footnotes

Note 1: Rob Bishop is roughly within the mainstream of House Republicans, with two-thirds of Republicans more liberal and one-third more conservative. Chaffetz is far to the right of the Republican party generally, with 93% of House Republicans to his left and only a handful to his right.

The comparison of Matheson to Bishop and Chafetz using “The DW-NOMINATE scores” doesn’t even come close to answering the question about Matheson being liberal or conservative. It only indicates who voted their party’s line. One can infer from Matheson’s lack of party voting (which means not voting for liberal issues) that he has voted conservativley. How conservative compared to the other two can’t be know from this data. Displaying the data this way however implies that Matheson is much more liberal than the other two- which is not supported by any of the data.

I think you’re talking about the second figure? The DW-NOMINATE scores are in the first figure, not the second. The DW-NOMINATE scores are far better than party support scores. For one thing, party support scores can’t differentiate between a Bernie Sanders (a self-proclaimed socialist who votes against his party when it’s not liberal enough) and a Jim Matheson (who votes against his party under the opposite circumstance.) These are not party support scores.

It’s true that the second figure is more similar to party support scores, but I wasn’t using the second figure to argue whether Matheson is liberal or conservative, only to show that he’s less predictable in his voting. The first figure is far more relevant.

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